Presented below is a composite list of Art. 29 cases reporting UNCITRAL Digest cases and other Art. 29 cases. All cases are listed in chronological sequence, commencing with the most recent. Asterisks identify the UNCITRAL Digest cases, commencing with the 5 October 1999 citation reported below. Cases are coded to the UNCITRAL Thesaurus.

English texts and full-text English translations of cases are provided as indicated. In most instances researchers can also access UNCITRAL abstracts and link to Unilex abstracts and full-text original-language case texts sourced from Internet websites and other data, including commentaries by scholars to the extent available.

(1) A contract may be modified or terminated by the mere agreement of the parties.

(2) A contract in writing which contains a provision requiring any modification or termination by agreement to be in writing may not be otherwise modified or terminated by agreement. However, a party may be precluded by his conduct from asserting such a provision to the extent that the other party has relied on that conduct.

1. The provision concerns the modification (which includes additions) [1] and termination of an already concluded contract through agreement of the parties. According to article 29(1), the mere consent of the parties is sufficient to effect any variation of the contract. If the parties have, however, agreed in writing on a written form for a modification or termination of their contract paragraph 2 provides that the contract then cannot be modified or terminated otherwise unless and to the extent that it would be inequitable to invoke the form requirement.

2. The provision does, and is intended to,[2] abolish the doctrine of "consideration" of the common law as far as the Convention applies.

3. An agreement is needed in order for the parties to be able to change a contract provision or to terminate their contract. The existence of such an agreement is determined on the basis of the provisions to be found in Part II (articles 14-24) of the Convention.[3] Article 29 provides that a contract can be modified purely by the agreement of the parties. In line with article 18(1), it was stated that mere silence of one party to proposals of the other to modify does not in itself amount to acceptance,[4] however it has also been stated that there was agreement as to the termination of a contract where a buyer refused to pay due to alleged non-conformity and subsequently the seller offered to market the goods itself, an offer to which the buyer did not reply.[5] One court stated that, although on the basis of article 29 CISG a contract could be modified purely by agreement of the parties, the modification of the purchase price could not result merely from the general mood of a meeting.[6] The acceptance without comment of a bill of exchange as payment has, however, been regarded as implied consent to a postponement of the date for payment provided for in the contract until the maturity of the bill.[7]

4. The interpretation of the parties' agreement as to the modification or termination of the contract is based on the Convention's rules on construction (in particular article 8).

5. The agreement of both parties is all that is required in order to modify or terminate their contract.[8] No form requirements must be met [9] unless the reservation concerning form applies (arts. 11, 12, 96) [10] or unless the parties have agreed otherwise. When article 96 applies, modifications agreed upon only orally are invalid.[11] For all other cases it follows from article 11 as a general principle of the Convention that the parties are free to modify or terminate their contract in any form be it either in writing or orally or in any other form. Even an implied termination of the contract has been held possible;[12] furthermore, it has been held that a written contract may be orally changed.[13]

6. According to article 29(2), a written or oral contract may generally be modified or terminated orally or in writing. If, however, a written contract contains a provision that any modification or termination of the contract must be in writing ("no oral modification"-clause or "written modification"-clause) then the parties cannot modify or terminate the contract in a different way.[14] An oral variation would be ineffective if invoked by one party in such a case unless article 29(2)(2) were to apply.[15]

7. A so-called merger clause according to which the complete contents of prior negotiations is merged in the contract document has been treated like a "no oral modification"-clause.[16] Therefore no evidence of oral agreements prior to the written contract could be adduced in order to modify or terminate that contract.

8. Article 29(2)(2) provides that a "no oral modification"-clause cannot be invoked by a party who by its conduct aroused the impression not to rely on the clause while, and to the extent that, the other party relied upon that conduct. It was stated that the provision is an expression of the general good faith principle that governs the Convention (art. 7(1)).[17]

FOOTNOTES

* The present text was prepared using the full text of the decisions cited in the Case Law on UNCITRAL Texts (CLOUT) abstracts and other citations listed in the footnotes. The abstracts are intended to serve only as summaries of the underlying decisions and may not reflect all the points made in the digest. Readers are advised to consult the full texts of the listed court and arbitral decisions rather than relying solely on the CLOUT abstracts.

[Citations to cisgw3 case presentations have been substituted [in brackets] for the case citations provided in the UNCITRAL Digest. This substitution has been made to facilitate online access to CLOUT abstracts, original texts of court and arbitral decisions, and full text English translations of these texts (available in most but not all cases). For citations UNCITRAL had used, go to <http://www.uncitral.org/english/clout/digest_cisg_e.htm>.]

2. See Secretariat Commentary to (then) article 27 ("overcoming the common law rule that "consideration" is required") Commentary on the draft Convention on Contracts for the International Sale of Goods, A/CONF.97/5, reproduced in United Nations Conference on Contracts for the International Sale of Goods: Official Records, at p. 28, paras. 2-3.

The Interpretive Turn in International Sales Law:
An Analysis of Fifteen Years of CISG Jurisprudence

Article 29 allows contracts to be modified or terminated by the "mere agreement" of the parties. This
provision reinforces the principle that no particular form is required for either modification or
termination.[153] Oral terminations or modifications, however, are ineffective if the parties have
previously prescribed formalities to such acts. National courts will find modifications to be invalid
in at least three situations. First, when the modification does not represent "agreement" by the
parties. Second, when [page 331] a writing is required because one of the parties has its place of
business in a Contracting State that made a declaration pursuant to Articles 12 and 96. In such a
situation Article 29 prohibits oral modifications.[154] Third, when the parties include a no oral
modification clause in a written contract.

Just as intent is critical in determining the existence or scope of a contract under Article 11, so intent
is important in examining the validity of a modification. Whether or not the parties have agreed on
the modification is a question that incorporates the offer and acceptance rules under Articles 14, 18,
and 19, as well as interpretation rules under Articles 8 and 9. A U.S. court in Chateau des Charmes
Wines Ltd. v. Sabate USA Inc. found that one party's unilateral attempt to modify an agreement failed
where there was no indication that the other party accepted or agreed to the new terms.[155] The
parties had orally agreed to the essential terms of the contract, but a forum selection clause which was
not part of the original agreement, was included in subsequent invoices.[156] According to the
court, it would be illogical to make the forum selection clause contained in the invoices part of the
contract.[157] The court stated that "[n]othing in the Convention suggests that the failure to
object to a party's unilateral attempt to alter materially the terms of an otherwise valid agreement is
an 'agreement' within the terms of Article 29."[158] The court took into account the various
circumstances recommended in Article 8(3) to determine the parties' intent, but concluded that there
was no evidence or conduct that indicated the party had agreed to the modifications added to the
invoice.[159] Other courts have also insisted on evidence of an agreement. For example, a
French court considered affidavits from the buyers' witnesses who were present at a meeting to
determine whether the parties had concluded a valid price modification.[160][page 332] Because
the affidavits did not mention the seller's agreement to the price, however, the court held that "the
modification of a sale price cannot result from the general environment of a meeting."[161]

Parties may avoid parol evidence difficulties such as those raised in the previous section by inserting
a merger or no oral modification clause that "extinguishes any and all prior agreements and
understandings not expressed in the writing."[162] Enforcing such clauses preserves the intent
of the parties as well as the Convention's principle of freedom of contract. The exception to Article
29's general rule, however, is that a "party may be precluded by his conduct from asserting such a
provision to the extent that the other party has relied on that conduct."[163] Several decisions
indicate that national courts respect clauses that prohibit oral modifications or the use of extrinsic
evidence, where there is no evidence that one party acted in a manner to induce reliance on oral
modifications.[164] Nevertheless, where a no oral modification or merger clause exists, a party
is allowed to establish conduct, such as a course of dealing, to override the modification clause.
[165] Despite academic concerns about the difficulty of interpreting Article 29(2), cases
addressing the issue have yet to surface.[166]

Article 29 allows contracts to be modified or terminated by the "mere agreement" of the parties. The
Secretariat's Commentary indicates that this [page 333] provision overcomes the common law
requirement of consideration.[167] At least one U.S. court as well as the Court of Arbitration
of the International Chamber of Commerce have recognized that under the CISG, a contract for the
sale of goods may be modified without consideration.[168] In one recent U.S. decision, however,
the court approached the consideration issue as a question of contract validity, which Article 4 of the
CISG specifically states is not governed by the Convention.[169] This is a questionable extension
of the validity delegation under Article 4. Article 29 brings contract modification within the scope
of the CISG. The specific default rules of Article 29, namely no writing or consideration
requirements, preempts the more general charge that issues of validity are to be determined by
national law. [page 334]

154.See Vestnik Vysshego Arbitrazhnogo Suda RF [Highest Court of Arbitration][Vestn.
Vyssh. Arb. Suda RF], Information Letter 29, Feb. 16, 1998 (Russ.), available at <http://cisgw3.law.pace.edu/cases/980216r1.html> (modification by telephone not valid where buyer had its
place of business in the Russian Federation and the former U.S.S.R. had made a declaration in
accordance with Articles 12 and 96); Vestn. Vyssh. Arb. Suda RF, Res. No. 4670/96, Mar. 25, 1997
(Russ.), available at <http://cisgw3.law.pace.edu/cases/970325r2.html> (modification of terms of
delivery must be in writing); Vital Berry Marketing NV v. Dira-Frost NV, AR 1894/94, Rechtbank
van Koophandel, Hasselt, May 2, 1995 (Belg.) available at
[<http://cisgw3.law.pace.edu/cases/950502b1.html>] (attempt to modify price
not valid where seller was from Chile, a State which had made declaration under Articles 12 and 96).

164.See Graves Import Co., 1994 U.S. Dist. LEXIS 13393 at *13; ICC Court of Arbitration -- Zurich Arbitral Awards, 9117, (Mar. 1998), available at
[<http://cisgw3.law.pace.edu/cases/989117i1.html>] (arbitral tribunal compared
Article 29(2) to UNIDROIT principles, Articles 2.17 and 2.18 to reach conclusion that a party could
not rely on oral promises, assurances, or writings not included in the contract and that there was no
reason to apply the exception clause which prevents a party from making use of the no oral
modification clause if its conduct would lead the other party to rely); Cong ty Ng Nam Bee v. Cong
ty Thuong mai Tay Ninh, People's Supreme Court, Appeal Division in Ho Chi Minh City, 74/VPPT,
Apr. 5, 1996 (Vietnam), available at
[<http://cisgw3.law.pace.edu/cases/960405v1.html>] (holding that letter of credit is a
type of extrinsic evidence, inadmissible to contradict contract terms where parties had a 'four-corner
clause').

166.See generally, Robert A. Hillman, Article 29(2) of the United Nations Convention on Contracts for the International Sale of Goods: A New Effort at Clarifying the Legal Effect of "No Oral Modification" Clauses, 21 Cornell Int'l L.J. 449 (1988) (reviewing problems raised by no oral
modifications and suggesting that new drafters take an approach that compromises less by either
enforcing or abolishing such clauses) [available at <http://cisgw3.law.pace.edu/cisg/biblio/hillman2.html>].

169.See Geneva Pharm. Tech. Corp., 201 F. Supp. 2d at 282-83 (court used New Jersey law
to determine whether there was consideration). See generally, Helen Elizabeth Hartnell, Rousing the
Sleeping Dog: The Validity Exception to the Convention on Contracts for the International Sale of
Goods, 18 Yale J. Int'l L. 1, 45 (1993) (proposing that courts seek a middle course in approaching
the validity issue, looking to domestic to determine whether an issue is one of validity but also
considering the international aspect of the CISG) [available at <http://cisgw3.law.pace.edu/cisg/biblio/hartnell.html>]; Gyula Eörsi, Problems of Unifying Law on the
Formation of Contracts for the International Sale of Goods, available at
<http://cisgw3.law.pace.edu/cisg/text/eorsi29.html> (recognizing that lack of consideration could be a
validity issue but that it is more likely that contract formation does not require consideration, a
conclusion which he maintains is supported by "the fact that the question did not even surface, in
connection with the 1964 Hague Convention on Formation (ULF)").

a. Article 29 of the CISG deals with the requirements for the modification and termination of
contracts. It further entrenches the principles of party autonomy, freedom of contract and
freedom from formalities contained in article 11 of the CISG.[1] These principles also form the
foundation of the UNIDROIT Principles of International Commercial Contracts as expressed
in articles 1.1, 1.5 and 2.18 and should therefore form the governing principles in the
interpretation of any contract as well as its modification or termination.[2]

b. Article 2.18 of the UNIDROIT Principles in itself sheds little light on the interpretation or
augmentation of article 29 of the CISG as both articles are formulated in almost exactly the
same words, with one insignificant exception. Where article 2.18 of the UNIDROIT Principles
deals with the abuse of the written modification clause, it refers to the prohibition to rely on
such clause to the extent that the other party has "acted in reliance" on that conduct. The CISG
merely refers to the extent that the other party has "relied on that conduct." It is submitted that
nothing turns on this divergence as reliance in itself implies some action or failure to act on the
part of that party.

c. In interpreting the scope of article 2.18 of the UNIDROIT Principles, regard should also be
had to the provisions of article 3.2 which deals with freedom of form and formalities. In the
Comments it is stated that mere agreement between the parties is sufficient for the valid
conclusion, modification and termination of agreements without any further requirements to be
found in domestic law. Specific reference is made to the fact that the requirement of
consideration, which may be applicable in common law legal systems, is excluded. This is in
conformity with the approach taken in the CISG.[3]

d. The first object of both article 29 CISG and article 2.18 of the UNIDROIT Principles is to
reinforce the principle that any agreed modification or termination will be valid in whatever form
it is made or contained.[4] Its second object is also to eliminate an important difference in
approach between civil and common law, namely clearly establishing that no consideration is
necessary for any amendment to be valid.[5] However, it also entrenches the time honored
principle that where parties have by agreement voluntarily restricted their ability to modify or
terminate a contract by requiring formalities for such actions, that agreement will be valid and
enforceable.[6]

e. The commentary to article 2.18 of the UNIDROIT Principles makes it clear that the second
object of the article is to generally render oral modifications or terminations void where parties
have prescribed formalities, thereby rejecting the idea that such modification or termination may
be viewed as an implied abrogation of the written modification or termination clause. This
approach confirms the same interpretative conclusion reached by Schlechtriem in respect of
Article 29 CISG.[7]

f. Both article 29 CISG and article 2.18 of the UNIDROIT Principles seem to apply only where
the modification or restriction clause is contained in a "written agreement."[8] In interpreting
what constitutes a "written agreement," the UNIDROIT Principles may be helpful as article 13
CISG only extends the concept of writing to telegrams and telexes. Article 1.10 of the
UNIDROIT Principles extends the meaning of written to "any mode of communication that
preserves a record of the information contained therein and is capable of being reproduced in
tangible form." It is generally recognized that article 13 CISG contains a gap in that it only
refers to older forms of technology and does not provide for more modern forms of electronic
communications such as e-mail, fax or Internet communications.[9] It is suggested that the
meaning of "written" should be extended to include these forms of communications in
accordance with the definition contained in article 1.10 of the UNIDROIT Principles.[10] It has
the advantage of being clear, practical and technologically neutral without losing sight of the
object of the written formality, namely preserving an objective reproducible record of the
communication between the parties.

g. The issue of merger clauses is not dealt with in these remarks as they are more appropriately
covered under article 8 CISG which deals with the interpretation and proof of agreements.[11]

h. The exception created in article 29(2) CISG is one area where the application of article 29
may lead to interpretational difficulties.[12] The rule is based on principles contained in the so-called "Mißbrauchseinwand" of German law, or the "nemo suum venire contra factum
proprium" principle of Roman law, or the doctrine of waiver and estoppel of Anglo-American
law.[13]

i. The illustrations contained in the Comments to article 2.18 of the UNIDROIT Principles may
be helpful in the interpretation of article 29 CISG in this regard. See also the examples
mentioned by Schlechtriem.[14] It may be asked, however, whether the Comments call for a
further requirement not specifically contained in article 2.18 of the UNIDROIT Principles,
namely that the reliance must have been reasonable under the circumstances.[15] It would seem
that this requirement is justifiable viewed in the light of the principle of good faith. Where
reliance was not reasonable under the circumstances, a party ought not to be allowed to use the
defense contained in article 29(2).[16]

j. Neither the CISG nor the UNIDROIT Principles makes provision for the case where the
parties have agreed to further formalities such as signature or witnesses for an amendment or
termination.[17] It is submitted that it would be in accordance with the provisions of article 29
CISG and 2.18 of the UNIDROIT Principles that the parties be held bound to such formalities
and that non-complying modifications or terminations would be void, unless the abuse exception
contained in article 29(2) CISG and 2.18 of the UNIDROIT Principles should apply.[18]

a. Article 29 of the CISG deals with the requirements for the modification and termination
of contracts. It further entrenches the principles of party autonomy, freedom of contract
and freedom from formalities contained in article 11 of the CISG.[1] These principles also
form the foundation of the Principles of European Contract Law ('"PECL") as expressed
in articles 1:102, 2:101(2) and 2:106 and should therefore form the governing principles in
the interpretation of any contract as well as its modification or termination.[2] Art 1:102
PECL however, pertinently subjects the principle of freedom of contract to the principle of
good faith and fair dealing, which may not be excluded.[3]

b. The first object of article 29 CISG is to reinforce the principle that any agreed
modification or termination will be valid in whatever form it is made or contained.[4] Its
second object is also to eliminate an important difference in approach between civil and
common law, namely clearly establishing that no consideration is necessary for any
amendment to be valid.[5] However, it also entrenches the time honored principle that where
parties have by agreement voluntarily restricted their ability to modify or terminate a
contract by requiring formalities for such actions, that that agreement will be valid and
enforceable.[6]

c. Article 2:106 PECL which deals with written modification clauses, differs somewhat
from article 29 CISG in that it merely creates a presumption of invalidity where there is a
clause requiring formalities for modification or termination.[7] There is, therefore, an
evidentiary onus on the party who wants to rely on an oral modification or termination to
prove that the parties nevertheless intended such modification or termination despite not
complying with the agreed formalities. This approach, which is less strict than the approach
found in the CISG, is based on the principle of good faith.[8]

d. The application of the principle of good faith may as a consequence be useful in
interpreting article 29 CISG, especially in respect of the abuse exception in article 29(2).
Where the reliance of a party on the written modification or termination clause would be
against the dictates of good faith under the circumstances, such reliance ought not to be
countenanced.[9]

e. Although the PECL does not specifically state that contracts may be informally modified
or terminated, it is clear from the provisions of article 2:101(2), which entrenches the
freedom of form, and article 2:106(1) that that is the actual point of departure in these
principles. The CISG and the PECL therefore are based on the same principle of freedom
of formalities as a starting point.

f. The PECL, however, does not accord the same strong effect to oral modification clauses
as the CISG as outlined in paragraph b. above. It may therefore well result in the PECL
following a more lenient approach than the CISG. An informal agreement to modify or
terminate a contract may therefore be interpreted as "an implied abrogation" of the clause
itself in terms of the PECL, whereas this is not the case with the CISG.[10]

g. Both article 29 CISG and article 2:106 PECL seem to apply only where the modification
or restriction clause is contained in a "written agreement."[11] In interpreting what constitutes
a "written agreement" the PECL may be helpful as article 13 CISG only extends the concept
of writing to telegrams and telexes. Article 1:301 PECL defines "written statements" as
"[including] communications made by telegram, telex, telefax, and electronic mail and other
means of communications capable of providing a readable record of the statement on both
sides." A readable record produced by a telephone receiver which is capable of converting
sound into writing is not a written statement under Article 1:301(6).[12] It is generally
recognised that article 13 CISG contains a gap in that it only refers to older forms of
technology and does not provide for more modern forms of electronic communications such
as e-mail, fax or internet communications.[13] It is suggested that the meaning of "written"
should be extended to include these forms of communications in accordance with the
definition contained in article 1:301 PECL.[14] The latter has the advantage of being clear,
practical and technologically neutral without losing sight of the object of the written
formality, namely preserving an objective reproducible record of the communication
between the parties.

h. The issue of merger clauses is not dealt with in these remarks as they are more
appropriately covered under article 8 CISG which deals with the interpretation and proof
of agreements.[15]

i. The exception created in article 29(2) CISG is one area where the application of article
29 may lead to interpretational difficulties.[16] The rule is based on principles contained in the
so-called "Mißbrauchseinwand" of German law or the "nemo suum venire contra factum
proprium" principle of Roman law or the doctrine of waiver and estoppel of Anglo-American law.[17]

j. Under article 2:106 PECL, it is required that the reliance by the party acting upon the informal modification or termination must have been reasonable. It would seem that this
requirement is justifiable also in respect of the CISG viewed in the light of the principle of
good faith.[18] Where reliance was not reasonable under the circumstances, a party ought not
to be allowed to use the defense contained in article 29(2) CISG.[19] The requirement of
reasonableness under the PECL is further refined in article 1:302 of the PECL.[20] In
considering what is "reasonable", it should be asked what persons under the same
circumstances and acting in good faith would have considered to be reasonable. In deciding
what is "reasonable", all relevant factors should be taken into consideration, including the
nature and purpose of the contract, the circumstances of the case and the usages and
practices of the trade or profession.[21] These generally reflect the behavior of reasonable
parties. This test could equally well be utilized in respect of the CISG.[22]

k. A further issue which crops up is whether the provisions of the exception in article 29(2) can be upheld in circumstances where writing is obligatory due to a country making a reservation in terms of article 96 of the CISG to article 12.[23] It is suggested that even in those instances oral modifications or terminations should be upheld where article 29(2) circumstances are found.[24] The decision in Belgium 2 May 1995 District Court Hasselt [25], however, seems to indicate that courts would be willing to apply the exception even in those instances.

l. Neither the CISG nor the PECL makes provision for the case where the parties have
agreed to further formalities such as signature or witnesses for an amendment or
termination.[26] In this respect there may be a divergence between the approach of the CISG
and the PECL. It is submitted that it would be in accordance with the provisions of article
29 CISG that the parties are held bound to such formalities and that non-complying
modifications or terminations would be void, unless the abuse exception contained in article
29(2) CISG should apply.[27] In filling the gap under article 2:106(1) it is submitted that in
accordance with the basic premises of that article, such requirements will only constitute a
presumption and will not be valid and binding per se as under the CISG. This divergence
is a result of the more lenient approached followed in terms of the PECL outlined in
paragraphs b. and f. above.